The invention relates to a venting system for an automobile vehicle fuel tank.
The invention relates more particularly to a venting system for an automobile vehicle fuel tank, of the type including a chamber which communicates with the tank and, via an outlet orifice at the top, with a vent pipe, which system includes, inside the chamber, a float which controls a needle valve for closing the top outlet orifice if the fuel level in the chamber exceeds a predetermined threshold.
The fuel tank of an automobile vehicle is vented to prevent any positive or negative pressure in the tank which would otherwise risk deforming it greatly.
Accordingly, as the tank is emptied of fuel, it is necessary to admit air into the tank to prevent the pressure therein falling unduly. In contrast, if the tank is exposed to a high temperature rise, for example if the vehicle is parked in direct sunlight, the pressure of the vapor contained in the tank can increase greatly and it is then necessary to evacuate some of the vapor to the outside.
It is also necessary to prevent fuel escaping from the venting system if the level of fuel near the system increases significantly, for example due to acceleration of the vehicle.
To this end, the document EP-A-0 254 631 has already proposed a venting system including a float which is adapted to urge a needle valve upward if the fuel level reaches the system, the needle then closing the exit orifice of the valve to prevent fuel leaking.
However, it has become apparent that a system of the above kind has shortcomings. When the vehicle is moving, the fuel sloshes around and can splash onto the system. Either such splashing can cause unnecessary closure of the top orifice, which can prevent correct venting of the tank, or the splashing avoids the float and reaches the outlet orifice before it is closed, with the risk that it may escape to the outside.
An object of the invention is therefore to propose an improved system which avoids these drawbacks.
To this end, the invention proposes a venting system for an automobile vehicle fuel tank, of the type including a chamber which communicates with the tank and, via an outlet orifice at the top, with a vent pipe, which system includes, inside the chamber, a float which controls a needle valve for closing the top outlet orifice if the fuel level in the chamber exceeds a predetermined threshold, characterized in that the system includes means between the tank and the float for limiting the speed of the fuel before it comes into contact with the float.
According to other features of the invention:
the means for limiting the speed of the fuel include a filter member;
the means for limiting the speed of the fuel include an apertured plate;
the means for limiting the speed of the fuel include chicanes;
the chamber is delimited at the bottom by a bottom transverse wall which has a bottom orifice communicating with the tank and the means for limiting the speed of the fuel are under the bottom transverse wall, between it and the tank;
the bottom transverse wall of the chamber takes the form of a part attached to a casing of the system and the attached part includes means for fixing the means for slowing the fuel;
the attached part includes a cylindrical skirt which extends axially downward from a peripheral. edge of the bottom transverse wall and delimits a housing open at the bottom receiving the means for slowing the fuel;